Indeterministic EAP error

Phil Mayers p.mayers at
Thu Oct 4 18:09:35 CEST 2012

On 04/10/12 16:45, Matthias Nagel wrote:
> I cannot find any pattern, so I do not believe it to be a client side
> issue.
> Of course, one can argue to ignore the warning as it works most of
> the time, but I do not like indeterministically behaving IT systems,
> hence it preys on my mind.
> Has anybody an idea what the reason might be? If anybody wants to see
> a full debug output or a tcpdump, I can provide you with plenty of
> that. But I could not find anything.

One thing: that logging only happens in "debug" mode. Most people don't 
run in debug mode all the time, so as far as I know, it could be normal 
- maybe everyone sees failure rates of that order?

Anyway, first things - check your "eap {}" module config, specifically 
ensure that max_sessions is high enough to support your load, that 
timer_expire isn't too low, and if applicable, that your TLS session 
caching is ok (size, particularly).

Otherwise - I assume you are authenticating wireless clients?

Unfortunately, wireless is funky. Clients can stop doing the EAP 
exchange for all sorts of reasons - interference / packet loss, signal 
strength issues (they moved to a different AP), prompting the user for 
password / cert issuance, etc.

Are you able to determine where the EAP sessions have got to before they 
hang up? Are they still in TLS setup, or inner-tunnel? Does it hang up 
after e.g. the EAP-MSCHAP challenge?

Regrettably the "session did not finish" logging isn't great, so 
determining this is hard - I keep meaning to see if it can be improved 
e.g. log some attributes from the original packet, log the state of the 
EAP session, etc.

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